This invention relates to a secondary pressure spring to be installed behind a stationary star ratchet in the free hub of an existing design. Specifically, this invention makes active a stationary star ratchet and provides a fail safe from accidental losses in engagement, quicker engagement, less frictional resistance, and decreased noise when in the free wheel mode.
A rear bicycle hub is generally attached to the rim by a series of criss-crossed steel spokes and the wheels make up an integral part of the bicycle. A conventional rear bicycle hub, whether a road bike, a mountain bike, or a tandem bike, require some form of a drive assembly (free hub) to engage or disengage the hub from a drive mode or a free wheel mode. A rear hub generally contains bearings, an axle, some form of drive assembly (free hub), and an array of gears called a cog set that is driven by a chain and shifted via a rear derailer. The most common drive assembly uses two or three pawl ratchets inside of a steel guide ring. The pawls, which are the male portions of the assembly, are spring loaded and evenly spaced around the insertion part of the free hub. These pawls require that a cooperating ring which is the female portion of the assembly, has a series of unidirectional, evenly spaced, ramped teeth that allows the pawls to rotate within. As the free hub is rotated the forward direction (or drive mode) the pawls spring into the female ring""s unidirectional teeth and lock the free hub into engagement and the bicycle is propelled forward. Whether coasting down a hill (no pedaling but the bicycle is moving) or pedaling backwards, the free hub disengages and the ramped portion of the guide ring and pawls separate and the pawls float on the springs making a ratcheting noise, this is called a free wheel. This free hub mechanism is the quintessential element in today""s bicycles for freedom in quick engagement, pedal location, and coasting.
The failure of the rear hub drive assembly is frequently attributed to the breakage of the pawls and springs. Though these materials are hardened steel, over time the pawls can become weakened and break. There are a number of variables why hubs fail, but in particular, design inefficiencies are the main reasons. There is, therefore, a recognized need for a fail safe that will prevent the bicycle hub from failing while under load. It is the objective of the present invention to provide such a fail safe.
The present invention resides in the rear hub in a secondary pressure spring located behind a stationary star ratchet in the free hub, thus making the stationary star ratchet moveable. Since the original and current designs use only one pressure spring to keep positive the engagement and are very vulnerable to slipping and loss of engagement, the secondary pressure spring allows the once stationary star ratchet to move into the other sprung star ratchet preventing any loss of contact between the two star ratchets creating a fail safe or safety mechanism.
The secondary pressure spring was installed behind the stationary star ratchet by removing a circlip from behind the inboard bearing of the free hub. The inboard bearing was then shifted into the former position of the removed circlip, and a distance bushing between the two bearings in the free hub was reduced to allow the inboard bearing in the free hub to shift back. Then a spacer (of the same thickness of the material that was removed from the distance bushing) was installed in-between the steel spacer and the inboard hub shell bearing to maintain the correct tolerances when the hub was reassembled. All of this was necessary to create the space needed to accommodate the secondary pressure spring.
The results are: a fail safe (prevention of accidental disengagement), reduced frictional resistance, a quieter ratcheting noise, and quicker engagement. It improves the original and current designs by 70% and is adaptable in all past and current designs of many rear bicycle hubs.